548 CI BBC Advice

General engine tech -- Drag Racing to Circle Track

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fdicrasto
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Re: 548 CI BBC Advice

Post by fdicrasto »

Why not. 820-840 hp.
TBART1970
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Re: 548 CI BBC Advice

Post by TBART1970 »

fdicrasto wrote:Why not. 820-840 hp.
Is that a serious, calculated guess?
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Re: 548 CI BBC Advice

Post by TBART1970 »

No guesses?
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MadBill
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Re: 548 CI BBC Advice

Post by MadBill »

It's like a woman asking you how old you think she is. Honesty is not the best policy. If you subtract too many years from your answer she knows it's B.S. but she doesn't mind. Thus the easy path is to go low on age, high on HP.

So here's me not taking my own advice: 790 HP @ 6,000, 750 lb-ft. @ 4,800.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
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Re: 548 CI BBC Advice

Post by TBART1970 »

739.9 hp at 6000
727.8 tq at 4800

I was hoping for 700-715. I am happy.
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Re: 548 CI BBC Advice

Post by MadBill »

Well at least I got the peak revs right... #-o
Felix, qui potuit rerum cognscere causas.

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Re: 548 CI BBC Advice

Post by TBART1970 »

Thanks everyone for all the help. Letting me know about the head flow deficiency and cam advice.
Now to get it back in the car and start tuning again.
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Re: 548 CI BBC Advice

Post by TBART1970 »

If you look at my original Dyno sheet it made 663 hp and 720 tq. Engine builder said it is a stingy Dyno. Those higher numbers are with a 4 percent fudge factor. The new numbers are not with the fudge factor. I am happy with the numbers as printed.

Fudged 4 percent. 769.49 hp 756.91 tq.
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Re: 548 CI BBC Advice

Post by TBART1970 »

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Re: 548 CI BBC Advice

Post by TBART1970 »

cstraub wrote:Old dyno sheet....barton555.jpg
Yes old sheet.
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Re: 548 CI BBC Advice

Post by TBART1970 »

Ceralli's cam recommendation,

262 intake
267 exhaust

.710 lift

112 lobe separation.
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Re: 548 CI BBC Advice

Post by user-17438 »

cstraub wrote:You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

You put the old smaller cam in it the butt dyno will feel better.

Old Cam
.650/620
242/252
108 LSA

New Cam
.672/.672
252/261
110 LSA
you put in a bigger cam, and he will never think of putting the smaller cams back in it. how is the butt dyno going to tell you anything while your tires are spinning and you aren't moving forward?

I saw a shop take out a mid 270@.050 cam fom a 632bbc, they put In a 242@.050. the engine lost 300whp and picked up 200ft torque.. the car was not easy to drive. tires would just blow up in smoke at the crack of the throttle. this was a big tire car. 33x18 hoosiers.

Big engines need big cams to be streetable. I know because I build them. I work with certain cam companies when necessary, and they normally fall where my gut instinct tells me.

heck my work truck had a bigger cam in it than both of those and it was just a tiny 496 both lift and duration.

The Dyno looks like it wants more Carb.

But if the customer is happy, hes happy.
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Re: 548 CI BBC Advice

Post by TBART1970 »

MTENGINES wrote:
cstraub wrote:You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

You put the old smaller cam in it the butt dyno will feel better.

Old Cam
.650/620
242/252
108 LSA

New Cam
.672/.672
252/261
110 LSA
you put in a bigger cam, and he will never think of putting the smaller cams back in it. how is the butt dyno going to tell you anything while your tires are spinning and you aren't moving forward?

I saw a shop take out a mid 270@.050 cam fom a 632bbc, they put In a 242@.050. the engine lost 300whp and picked up 200ft torque.. the car was not easy to drive. tires would just blow up in smoke at the crack of the throttle. this was a big tire car. 33x18 hoosiers.

Big engines need big cams to be streetable. I know because I build them. I work with certain cam companies when necessary, and they normally fall where my gut instinct tells me.

heck my work truck had a bigger cam in it than both of those and it was just a tiny 496 both lift and duration.

The Dyno looks like it wants more Carb.

But if the customer is happy, hes happy.
Injected in the car.
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Re: 548 CI BBC Advice

Post by TBART1970 »

In the car and running, vacuum is up. Now time to tune with the Holley EFI.
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Re: 548 CI BBC Advice

Post by TBART1970 »

I pulled the distributor to check the gears, everything looks good. Oil pressure is good, car runs good. 130 miles on it, still tuning.
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